1. Field of the Invention:
This invention relates to protective eyewear such as goggles and safety glasses which can be of the prescription or non-prescription type. The invention finds particular use for the protection of persons exposed to the ultraviolet radiation produced during the process of electric arc welding.
2. Description of the Prior Art:
It is known to incorporate cerium dioxide into glass particularly for use in spectacle lenses to provide increased absorption of ultraviolet radiation in the wavelength range below about 350 nanometers. Such lenses are used, for instance, where it is desirable to protect the eyes against ultraviolet radiation present in sunlight at high altitudes, emanating from fluorescent type lighting fixtures or other ultraviolet light sources.
The use of cerium in glass has also been described by Weyl in the book Colored Glasses published by Society of Glass Technology, Sheffield, England, 1967, pages 229-234. Light absorption of a lead crystal glass containing cerium oxide and titanium oxide is shown on page 233 to be greatest between 500 and 700 nanometers wavelength.
It has long been known that silicate glasses can be stained by exposing them to specific mixtures of chemicals at elevated temperatures. In U.S. Pat. No. 3,424,567, there is described a process for staining a borosilicate glass which is free of reducing agents by employing glass staining compositions such as cuprous sulfide, silver oxide, vanadium pentoxide, zinc sulfide and calcium sulfite. The coloration is said to be produced as a result of the migration of the silver and copper ions into the glass structure in exchange for the alkali metal ions of the glass composition in the vicinity of the stained area. There is no indication that the exchange of alkali metal ions for silver and copper ions produces a stained glass composition having reduced ultraviolet absorption characteristics.